Intense pulsed light induced crystallization of a liquid-crystalline polymer semiconductor for efficient production of flexible thin-film transistors.

Here we demonstrated the split-second crystallization of a liquid-crystalline conjugated polymer semiconductor induced by irradiation with intense pulsed white light (IPWL) for the efficient improvement of electrical properties of flexible thin film transistors. A few seconds of IPWL irradiation of poly(didodecylquaterthiophene-alt-didodecylbithiazole) (PQTBTz-C12) thin films generated heat energy through the photo-thermal effect, leading to the crystallization of PQTBTz-C12 and formation of nodule-like nanostructures. The IPWL-induced crystallization of PQTBTz-C12 resulted in a threefold improvement in the field-effect mobility of thin film transistors compared to as-prepared devices. The conformational change of the PQTBTz-C12 chains was found to be strongly related to the irradiation fluence. As a proof-of-concept, the IPWL treatment was successfully applied to the PQTBTz-C12 layer in flexible transistors based on plastic substrates. The performance of these flexible devices was significantly improved after only 0.6 s of IPWL treatment, without deformation of the plastic substrate.

Switching Mechanisms of Nonvolatile Memory Devices Fabricated with a Polydopamine Layer.

Nonvolatile memory devices based on a polydopamine (PDA) layer were fabricated by using a dip-coating process. Atomic force microscopy images revealed that the PDA layer had a conformal surface. The energy dispersive X-ray data showed the atomic stoichiometry of nitrogen and carbon in the PDA layer. The capacitance-voltage (C-V) curves of the Al/PDA/n-Si memory devices at 300 K showed a hysteresis with a large flat band shift, indicating that the incomplete PDA layer acted as a charge storage in the memory device. The switching mechanisms for the writing and erasing processes for the Al/PDA/n-Si devices are described on the basis of the C-V results and the energy band diagrams.

Cervical subcutaneous emphysema and pneumomediastinum after septorhinoplasty.

Cervical and facial subcutaneous emphysema is mainly caused by maxillofacial trauma or head and neck surgery. There are only 2 cases of subcutaneous emphysema after septorhinoplasty in the English literature. We report a case of subcutaneous emphysema and pneumomediastinum after a septorhinoplasty.A healthy 35-year-old man with nasal obstruction and dissatisfaction with the shape of his nose was referred to our outpatient clinic. The patient had a septorhinoplasty including bilateral medial and lateral osteotomy under general anesthesia. On the fifth day after the surgery, the patient visited the emergency department with swelling and pain in the right submandibular area and cheek. On computed tomographic (CT) scans, air was observed in the right temporal space, masticator space, submandibular space, and superior mediastinal space. He was immediately hospitalized for administration of intravenous antibiotics and bed rest.On the fifth day after the hospitalization, follow-up CT scans were performed. Subcutaneous emphysema and pneumomediastinum were markedly decreased. The patient was discharged on the fifth day.

Porous polyimide membranes prepared by wet phase inversion for use in low dielectric applications.

A wet phase inversion process of polyamic acid (PAA) allowed fabrication of a porous membrane of polyimide (PI) with the combination of a low dielectric constant (1.7) and reasonable mechanical properties (Tensile strain: 8.04%, toughness: 3.4 MJ/m3, tensile stress: 39.17 MPa, and young modulus: 1.13 GPa), with further thermal imidization process of PAA. PAA was simply synthesized from purified pyromellitic dianhydride (PMDA) and 4,4-oxydianiline (ODA) in two different reaction solvents such as γ-butyrolactone (GBL) and N-methyl-2-pyrrolidinone (NMP), which produce Mw/PDI of 630,000/1.45 and 280,000/2.0, respectively. The porous PAA membrane was fabricated by the wet phase inversion process based on a solvent/non-solvent system via tailored composition between GBL and NMP. The porosity of PI, indicative of a low electric constant, decreased with increasing concentration of GBL, which was caused by sponge-like formation. However, due to interplay between the low electric constant (structural formation) and the mechanical properties, GBL was employed for further exploration, using toluene and acetone vs. DI-water as a coagulation media. Non-solvents influenced determination of the PAA membrane size and porosity. With this approach, insight into the interplay between dielectric properties and mechanical properties will inform a wide range of potential low-k material applications.

Spin-flip-driven anomalous Hall effect and anisotropic magnetoresistance in a layered Ising antiferromagnet.

The influence of magnetocrystalline anisotropy in antiferromagnets is evident in a spin flip or flop transition. Contrary to spin flops, a spin-flip transition has been scarcely presented due to its specific condition of relatively strong magnetocrystalline anisotropy and the role of spin-flips on anisotropic phenomena has not been investigated in detail. In this study, we present antiferromagnet-based functional properties on an itinerant Ising antiferromagnet Ca0.9Sr0.1Co2As2. In the presence of a rotating magnetic field, anomalous Hall conductivity and anisotropic magnetoresistance are demonstrated, the effects of which are maximized above the spin-flip transition. Moreover, a joint experimental and theoretical study is conducted to provide an efficient tool to identify various spin states, which can be useful in spin-processing functionalities.

Spin-flip-driven reversal of the angle-dependent magnetic torque in layered antiferromagnetic Ca0.9Sr0.1Co2As2.

Spin-flip transition can occur in antiferromagnets with strong magnetocrystalline anisotropy, inducing a significant modification of the anisotropic magnetic properties through phase conversion. In contrast to ferromagnets, antiferromagnets have not been thoroughly examined in terms of their anisotropic characteristics. We investigated the magnetic-field and angle-dependent magnetic properties of Ising-type antiferromagnetic Ca0.9Sr0.1Co2As2 using magnetic torque measurements. An A-type antiferromagnetic order emerges below TN = 97 K aligned along the magnetically easy c-axis. The reversal of the angle-dependent torque across the spin-flip transition was observed, revealing the strong influence of the magnetocrystalline anisotropy on the magnetic properties. Based on the easy-axis anisotropic spin model, we theoretically generated torque data and identified specific spin configurations associated with the magnetic torque variation in the presence of a rotating magnetic field. Our results enrich fundamental and applied research on diverse antiferromagnetic compounds by shedding new light on the distinct magnetic features of the Ising-type antiferromagnet.

Multi-pulsed white light sintering of printed Cu nanoinks.

Pulse management of white light to maximize the sintering efficiency of a rapid (msec) and substrate-protective method, intense pulsed light (IPL), was studied systematically with a printable Cu nanoink. An excessive pulse energy that induces deleterious defects on the Cu film along with damage on a plastic substrate was dissipated into multiple sub-pulses while maintaining a total energy budget over the threshold level for successful Cu sintering. Electrical properties of the metal layers were analyzed in conjunction with pulse formation factors such as average energy, pulse duration, peak power and pulse number to determine their respective effects on IPL sintering. In the quantitative results, the optimized sintering conditions of copper nanoparticles with a mean diameter of 30 nm and a fixed total irradiated pulse energy of 32 J cm(-2) were a pulse number and pulse width of > 4 and < 3 msec, respectively.

Behavior of magnetoelectric hysteresis and role of rare earth ions in multiferroicity in double perovskite Yb2CoMnO6.

Double-perovskite multiferroics have been investigated because alternating orders of magnetic ions act as distinct magnetic origins for ferroelectricity. In Yb2CoMnO6, the frustrated antiferromagnetic order emerging at TN = 52 K induces ferroelectric polarization perpendicular to the c axis through cooperative O2- shifts via the symmetric exchange striction. In our detailed measurements of the magnetoelectric properties of single-crystalline Yb2CoMnO6, we observe full ferromagnetic-like hysteresis loops that are strongly coupled to the dielectric constant and ferroelectric polarization at various temperatures below TN. Unlike Lu2CoMnO6 with non-magnetic Lu3+ ions, we suggest the emergence of additional ferroelectric polarization along the c axis below the ordering temperature of magnetic Yb3+ ions, TYb ≈ 20 K, based on the spin structure established from recent neutron diffraction experiments. While the proposed description for additional ferroelectricity, ascribed to the symmetric exchange striction between Yb3+ and Co2+/Mn4+ magnetic moments, is clearly given, anomalies of dielectric constants along the c axis are solely observed. Our interesting findings on magnetoelectric hysteresis and the possible development of additional ferroelectricity reveal notable characteristics of double perovskites and provide essential guidance for the further examination of magnetoelectric functional properties.

Ag flake/silicone rubber composite with high stability and stretching speed insensitive resistance via conductive bridge formation.

High stability, stretchable speed insensitive properties, high stretchability, and electrical conductivity are key characteristics for the realisation of wearable devices. However, conventional research is mainly focused on achieving only high stretchability and electrical conductivity. Studies on the stability and stretching speed insensitive properties generally require complex fabrication processes, which are in need of further improvement. In this study, we propose a facile formation of a conductive bridge in composites by using surface damage and the viscoelastic property of the polymer. Surface cracks due to repeated stretching cycles formed conductive bridges via stress relaxation of the viscoelastic polymer matrix. The conductive bridge resulted in the conductor having highly stable resistance values at target strains and stretching speed insensitive resistance, even at stretching speeds that were 20 times faster than the minimum.

Layer-Selective Synthesis of MoS2 and WS2 Structures under Ambient Conditions for Customized Electronics.

Transition metal dichalcogenides (TMDs) have attracted significant interest as one of the key materials in future electronics such as logic devices, optoelectrical devices, and wearable electronics. However, a complicated synthesis method and multistep processes for device fabrication pose major hurdles for their practical applications. Here, we introduce a direct and rapid method for layer-selective synthesis of MoS2 and WS2 structures in wafer-scale using a pulsed laser annealing system (λ = 1.06 µm, pulse duration ∼100 ps) in ambient conditions. The precursor layer of each TMD, which has at least 3 orders of magnitude higher absorption coefficient than those of neighboring layers, rigorously absorbed the incoming energy of the laser pulse and rapidly pyrolyzed in a few nanoseconds, enabling the generation of a MoS2 or WS2 layer without damaging the adjacent layers of SiO2 or polymer substrate. Through experimental and theoretical studies, we establish the underlying principles of selective synthesis and optimize the laser annealing conditions, such as laser wavelength, output power, and scribing speed, under ambient condition. As a result, individual homostructures of patterned MoS2 and WS2 layers were directly synthesized on a 4 in. wafer. Moreover, a consecutive synthesis of the second layer on top of the first synthesized layer realized a vertically stacked WS2/MoS2 heterojunction structure, which can be treated as a cornerstone of electronic devices. As a proof of concept, we demonstrated the behavior of a MoS2-based field-effect transistor, a skin-attachable motion sensor, and a MoS2/WS2-based heterojunction diode in this study. The ultrafast and selective synthesis of the TMDs suggests an approach to the large-area/mass production of functional heterostructure-based electronics.

Two-in-One Device with Versatile Compatible Electrical Switching or Data Storage Functions Controlled by the Ferroelectricity of P(VDF-TrFE) via Photocrosslinking.

Organic electronics demand new platforms that can make integrated circuits and undergo mass production while maintaining diverse functions with high performance. The field-effect transistor has great potential to be a multifunctional device capable of sensing, data processing, data storage, and display. Currently, transistor-based devices cannot be considered intrinsic multifunctional devices because all installed functions are mutually coupled. Such incompatibilities are a crucial barrier to developing an all-in-one multifunctional device capable of driving each function individually. In this study, we focus on the decoupling of electric switching and data storage functions in an organic ferroelectric memory transistor. To overcome the incompatibility of each function, the high permittivity needed for electrical switching and the ferroelectricity needed for data storage become compatible by restricting the motion of poly(vinylidene fluoride-trifluoroethylene) via photocrosslinking with bis-perfluorobenzoazide. The two-in-one device consisting of a photocrosslinked ferroelectric layer exhibits reversible and individual dual-functional operation as a typical transistor with nonvolatile memory. Moreover, a p-MOS depletion load inverter composed of the two transistors with different threshold voltages is also demonstrated by simply changing only one of the threshold voltages by polarization switching. We believe that the two-in-one device will be considered a potential component of integrated organic logic circuits, including memory, in the future.

Low-Voltage Organic Transistor Memory Fiber with a Nanograined Organic Ferroelectric Film.

Wearable technology offers new ways to be more proactive about our health and surroundings in real time. For next-generation wearable systems, robust storage and recording media are required to monitor and process the essential electrical signals generated under various unpredictable strain conditions. Here, we report the first fibriform organic transistor memory integrated on a thin and flexible metal wire. A capillary tube coating system allows the formation of a thin and nanograined organic ferroelectric film on the wire. The uniform morphology imparts excellent switching stability (∼100 cycles), quasi-permanent retention (over 5 × 104 s), and low-voltage operation (below 5 V) to the fiber-shaped memory devices. When sewn in a stretchable textile fabric, the memory fiber achieves long retention time of more than 104 s with negligible degradation of memory window even under a constant diagonal strain of 100% that exhibits reliable data storage under tough environments. These results illustrate the possibility of the practical, wearable fiber memory for recording electronic signals in smart garment applications.

Light sintering of ultra-smooth and robust silver nanowire networks embedded in poly(vinyl-butyral) for flexible OLED.

A conductive, uniform, and ultra-smooth flexible transparent composite film is produced by embedding silver nanowires (AgNWs) into poly(vinyl-butyral) (PVB) without pressure or high-temperature annealing. The adhesion of AgNWs was greatly improved by embedding them in PVB, and surface roughness and sheet resistance (Rs) improvements were achieved through the use of the intense pulsed light (IPL) method, which welds the interconnections among AgNWs in a short time without heat or pressure treatment. The sheet resistance of PVB/AgNWs with the IPL(PAI) composite film reaches 12.6 ohm/sq with a transmittance of 85.7% (at 550 nm); no clear changes in the sheet resistance are observed after a substrate bending and tape test, suggesting excellent flexibility. In the case of PAI, the change in sheet resistance was only 2.6% after a 2,000-bend test, and the resulting bending radius was less than 1 mm. When IPL was exposed to PVB/AgNWs, the figure of merit was 2.36 times higher than that without exposure. Finally, flexible OLEDs using PAI exhibited comparable or higher electroluminescent characteristics than other devices with well-known flexible electrodes-including indium-zinc-oxide on polymer plastic-which is a promising discovery for flexible optoelectronic applications.

Flash-induced nanowelding of silver nanowire networks for transparent stretchable electrochromic devices.

Electrochromic devices (ECDs) are emerging as a novel technology for various applications like commercialized smart window glasses, and auto-dimming rear-view mirrors. Recently, the development of low-power, lightweight, flexible, and stretchable devices has been accelerated to meet the growing demand in the new wearable devices market. Silver nanowires (AgNWs) can become new primary transparent conducting electrode (TCE) materials to replace indium tin oxide (ITO) for ECDs. However, issues such as substrate adhesion, delamination, and higher resistance still exist with AgNWs. Herein, we report a high-performance stretchable flash-induced AgNW-network-based TCE on surface-treated polydimethylsiloxane (PDMS) substrates. A Xe flash light method was used to create nanowelded networks of AgNWs. Surface silane treatments increased the adhesion and durability of the films as well. Finally, ECDs were fabricated under the optimal conditions and examined under strained conditions to demonstrate the resistance and mechanical behaviours of the devices. Results showed a flexible and durable film maintaining a high level of conductivity and reversible resistance behaviour, beyond those currently achievable with standard ITO/PET flexible TCEs.

Ultrastretchable Conductor Fabricated on Skin-Like Hydrogel-Elastomer Hybrid Substrates for Skin Electronics.

Printing technology can be used for manufacturing stretchable electrodes, which represent essential parts of wearable devices requiring relatively high degrees of stretchability and conductivity. In this work, a strategy for fabricating printable and highly stretchable conductors are proposed by transferring printed Ag ink onto stretchable substrates comprising Ecoflex elastomer and tough hydrogel layers using a water-soluble tape. The elastic modulus of the produced hybrid film is close to that of the hydrogel layer, since the thickness of Ecoflex elastomer film coated on hydrogel is very thin (30 µm). Moreover, the fabricated conductor on hybrid film is stretched up to 1780% strain. The described transfer method is simpler than other techniques utilizing elastomer stamps or sacrificial layers and enables application of printable electronics to the substrates with low elastic moduli (such as hydrogels). The integration of printed electronics with skin-like low-modulus substrates can be applied to make wearable devices more comfortable for human skin.

Organic-inorganic hybrid nanomaterial as a new fluorescent chemosensor and adsorbent for copper ion.

Functionalized silica nanotube (FSNT) possessing the phenanthroline moiety as a fluorescent receptor was fabricated by solgel reaction, and the binding ability of FSNT with metal ions was evaluated by fluorophotometry.

Tongue Volume Influences Lowest Oxygen Saturation but Not Apnea-Hypopnea Index in Obstructive Sleep Apnea.

OBJECTIVES: The aim of this study was to identify correlations between sleep apnea severity and tongue volume or posterior airway space measured via three-dimensional reconstruction of volumetric computerized tomography (CT) images in patients with obstructive sleep apnea (OSA) for use in predicting OSA severity and in surgical treatment. We also assessed associations between tongue volume and Mallampati score. METHODS: Snoring/OSA male patients (n = 64) who underwent polysomnography, cephalometry, and CT scans were enrolled in this retrospective study. OSA was diagnosed when the apnea-hypopnea index (AHI) was greater than 5 (mild 5-14; moderate 15-29; severe>30). The patients were also categorized into the normal-mild group (n = 22) and the moderate-severe group (n = 42). Using volumetric CT images with the three-dimensional reconstruction technique, the volume of the tongue, posterior airway space volume, and intra-mandibular space were measured. The volumes, polysomnographic parameters, and physical examination findings were compared, and independent factors that are related to OSA were analysed. RESULTS: No associations between tongue volume or posterior airway space and the AHI were observed. However, multivariate linear analyses showed that tongue volume had significantly negative association with lowest O2 saturation (r = 0.365, p = 0.027). High BMI was related to an increase in tongue volume. Modified Mallampati scores showed borderline significant positive correlations with absolute tongue volume (r = 0.251, p = 0.046) and standardized tongue volume (absolute tongue volume / intramandibular area; r = 0.266, p = 0.034). Between the normal-mild and moderate-severe groups, absolute tongue volumes were not different, although the standardized tongue volume in the moderate-severe group was significantly higher. CONCLUSION: Absolute tongue volume showed stronger associations with lowest O2 saturation during sleep than with the severity of AHI. We also found that high BMI was a relevant factor for an increase in absolute tongue volume and modified Mallampati grading was a useful physical examination to predict tongue size.

Split-second nanostructure control of a polymer:fullerene photoactive layer using intensely pulsed white light for highly efficient production of polymer solar cells.

Intensely pulsed white light (IPWL) treatment was tested as an ultrafast, large-area processable optical technique for the control of the nanostructure of a polymeric bulk-heterojunction photoactive layer to improve the efficiencies of polymer solar cells. Only 2 s of IPWL irradiation of a polymer:fullerene photoactive layer under ambient conditions was found to enhance significantly the power conversion efficiencies of the tested polymer solar cells to values approaching that of typical devices treated with thermal annealing. Consecutive white-light pulses from the xenon lamp induce the self-organization of the polymeric donor into an ordered structure and result in the optimized phase segregation of the polymeric donor and the fullerene acceptor in the photoactive layer, which enhances the light absorption and hole mobility and results in efficient photocurrent generation. The effects of varying the pulse conditions on device performance, including the irradiation fluence, pulse duration time, and number of pulses, were systematically investigated. Finally, it was successfully demonstrated that the IPWL treatment produces flexible polymer solar cells. The proposed IPWL process is suitable for the efficient industrial roll-to-roll production of polymer solar cells.

Formation of a polymer particle monolayer by continuous self-assembly from a colloidal solution.

The preparation of two-dimensional monolayers of polymer particles over a large area was demonstrated via a facile solution process. Polymer microspheres were continuously self-assembled into a close-packed monolayer from a colloidal solution confined between two plates such that the top plate was carefully dragged at a constant velocity in the direction opposite that of the monolayer growth. In situ direct observation of the particle movement during the coating process confirmed that particle transport was directed toward the contact line of the solution meniscus by evaporation-induced convective flow. Sliding of the top plate apparently effectively counterbalanced the convective flow to provide the particles with a contact line for growth of a monolayer particle array. The influence of particle concentration, sliding speed of the top plate, and surface wettability of the bottom substrate were investigated and optimized. Monolayer particle arrays were successfully demonstrated as a template for the preparation of ZnO films with ordered hollow hemispherical structures. This approach is applicable to the fabrication of ordered structures of monodispersed particles composed of various materials over large areas.

Significance of the development of the inner ear third window effect after endolymphatic sac surgery in Ménière disease patients.

OBJECTIVES/HYPOTHESIS: The goal of this study was to identify the clinical significance of the low-frequency air-bone gap (LFABG) that often develops after endolymphatic sac surgery. STUDY DESIGN: Prospective study. METHODS: Sixteen patients who had been diagnosed with definite Ménière disease and underwent endolymphatic sac surgery were studied. The surgical outcome was evaluated based on the 1995 guidelines of the American Academy of Otolaryngology-Head and Neck Surgery. The number of patients who developed LFABGs (a mean air-bone gap >10 dB HL at 250, 500, and 1,000 Hz) after surgery was determined, and the significance of the LFABGs was evaluated by analyzing their relation with the surgical outcome. RESULTS: The vertigo spells of nine patients were completely controlled (class A). The number of vertigo spells was reduced by 60% to 99% in 6 patients (class B) and by 20% to 59% in 1 patient (class C). Postoperative LFABGs were observed in 13 patients. The mean LFABG of the patients in class A was significantly larger than that of the patients in classes B and C (25.0 ± 7.6 dB nHL in class A vs. 10.0. ± 7.5 dB nHL in class B and C; P = .005). CONCLUSIONS: Based on the data of the current study, we conjectured that the correlation of large LFABGs with excellent vertigo control in this study may be due to a third window phenomenon related to bony decompression of the endolymphatic sac and duct, and may serve as a favorable prognostic marker.